The oxidation of tea beverages such as tea and green tea and alcoholic beverages such as beer and sparkling liquor progresses with the passage of time after their production, so that their flavor gradually deteriorates. This is mainly due to oxygen entering these beverages in the process of their production. In the case of beer, for instance, if only an extremely small amount of oxygen enters the beer during its production process, the oxygen molecules are partially reduced by electrons transferred from metal (Fe, Cu) ions existing in the beer in its preserved state so that active oxygen is produced. The active oxygen oxidizes a variety of ingredients in the beer, such as isohumulone and alcohols, and generates aldehydes, which is the cause of aging odor, thereby deteriorating the flavor.